由於氣流停留在超音速燃燒衝壓引擎燃燒室之時間極短，對於燃燒室點火過程有極大的挑戰，是以嘗試採用氣閥(Air throttling)系統，在燃燒室之點火階段予以輔助，藉此增加點火成功率。本實驗以視流紋影法搭配壁面靜壓量測，觀察凹槽形式之超音速流場中的凹槽面氣閥噴注與平板面氣閥噴注之流場變化情況。從影像上可以發現，當氣閥噴注增強時，邊界層及剪切層之分離情形也隨之增加，而從壁面壓力數值可知氣閥噴注確實可造成噴注上游壁面壓力上升，並且隨著氣閥噴注強度增加，壓力上升之數值與影響範圍皆有所成長。比較凹槽面與平板面不同邊界層狀況受氣閥噴注之影響，可發現凹槽面受影響程度較高。最後透過影像觀察與實際量測到之增壓現象，可解釋氣閥噴注使流場壓力上升之根本原因為邊界層分離。

An experimental investigation of air throttling applied in supersonic cavity flow has been conducted. Different air throttling momentum flux has been used to realize the interaction between air throttling and supersonic cavity flow qualitatively. Cavity side air throttling injection and plate side air throttling injection has also been investigated. High-speed schlieren photography are implemented to explore boundary layer separation and shock system in transient and steady state. Wall pressure measurement along the test section is also used to help understanding pressure distribution in time and spatially. The higher air throttling momentum will get more intensive boundary layer separation, and thus get higher wall pressure increment. When the separation region height overtook throttling penetration height, a supersonic-diffuser-type flow pattern occurred, which caused wall pressure increased dramatically. Through transient observation, boundary layer separation is the main reason which lead to new shock system, and the shock propagation upstream is due to boundary layer separation region extending.

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